This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Protein arginylation is a poorly understood posstranslational modification that is essential for cardiovascular development and angiogenesis and possibly takes part in the normal functioning of other physiological systems and cell types. Evidence indicates that many proteins are arginylated in vivo;however the identity of these proteins is unknown. This collaboration is aimed to identify proteins arginylated in vivo.